1. Field of the Invention
This invention relates to a drive transmitting mechanism including damping springs for use in an internal combustion engine of a car, ship, etc.
2. Description of the Prior Art
A damping mechanism which is disclosed in Japanese Utility Model Application No. 55 (1980)-18110 comprises a coil spring and a seat for retaining the coil spring. The coil spring has two seats at both ends thereof and is circumferentially compressibly interposed between a drive plate and a driven plate, the latter connected to a flywheel. Each seat has concave and convex portions formed in semicircular shape and arranged to abut the drive plate or the driven plate. In cooperation with the concave and convex portions of the spring seat, the drive plate and the driven plate are provided with convex portions and concave portions, respectively. Elastic members are positioned solely at shoulder portions of the spring seat for the suppression of noise as the spring engages the drive plate or driven plate.
In practice, at low rotation speeds of the internal combustion engine, no striking sound occurs when the spring seat strikes the driven plate, due to the presence of the elastic members. However, during the starting or stopping of the engine, the striking noise occurs. It has been found by the present inventors that as the rotation rate of the engine passes through the range of the resonance frequency of the apparatus during the starting or stopping of the engine, a torque acts on the damping mechanism which is larger than the torque which would result solely from the low rotation rate of the engine. As a result, the bottom surface of the concave portion and the uppermost surface of the convex portion of the spring seat strike directly the drive plate or the driven plate, thereby producing appreciable noise.